PLANTS From Cells to Systems

1. PLANTSFrom Cells to Systems Plant Cells, Tissues, and Organs

2. This Chapter... • How plant cells specialize to form different kinds of plant tissues • Links between specialized cells, tissues, organs, and systems in plants • How plant organs work together to meet the needs of a plant

3. The process by which cells develop from similar cells into cells that have specific functions within a multicellular organism is called cell specialization. • The stage of development of a living organism during which specialized cells form is called cell differentiation.

4. Cell Differentiation • Cell differentiation results in cells being specialized for different functions or tasks. • Proteins, produced by genes, determine the function of a cell. Figure 1. Cells that are specialized for storing energy have large storage vacuoles Figure 2. Cells that are specialized for photosynthesis are packed with chloroplasts

5. Cells, Tissues and Organs • Groups of specialized cells form tissues, and groups of tissues work together in organsof a plant (such as roots, stems, and leaves) • Plants are always growing and producing new cells. Meristematic cells (or meristem) are responsible for this growth • Meristem constantly produce cells, which then become specialized, and combine to form three types of tissues: dermal tissue, ground tissue, and vascular tissue Figure 3: Meristem produce new cells that differentiate into the specialized cells that make up different plant tissues

6. Repair & Replacement • Plants, unlike multicellular animals, form new organs throughout their lives • For example, the leaves and roots of plants are continuously growing and being replaced Figure 4: Leaves become less efficient with age, and are replaced by new, more efficient leaves.

7. Meristematic cells are located at the tips of roots and branches, which results in the plants ability to grow up, down and out • Plants that produce leaves or flowers have buds. This is the swelling of a stem that contains meristem for a new, not yet developed tissue of a leaf or flower Terminal bud Lateral bud Figure 6: A plants most active growth occurs near the terminal bud. The lateral buds are dormant, but they have the potential to grow new branches, leaves and flowers.

8. Growing UP vs. Branching OUT Figure 7: The plant hormone, auxin, which is given off by growing areas of a plant (terminal bud), controls the cells below and behind them (lateral buds). This results in plants growing upward. However, if the terminal bud is removed, the plant will bush out at its lateral buds.

9. Plant • SHOOTS • Flower • Stem • Leaf • ROOTS

10. Plant Organs • Three types of organs make up the body of a plant: • Leaf • Stem • Root • A fourth organ is the reproductive organ, which is often the flower of a plant

11. The Leaf • The leaf is the site of photosynthesis. Many specialized cells of a leaf allow this organ to perform important functions

13. Upper and Middle Leaf • The upper surface of a leaf is dermal tissue called the epidermis. The epidermis secretes a waxy cuticle that helps reduce evaporation at the leaf’s surface. • In between the upper and lower leaf surface is the mesophyll tissue. Mesophyll tissue includes palisade and spongy parenchyma cells. • The palisade cells are arranged in a way that allow them to meet the Sun’s rays head on, allowing the rays to pass through the cell and meet the chloroplasts, where a lot of photosynthesis takes place. • The spongy parenchyma cells are loosely packed to form open spaces to allow for gas exchange of H2O(g) , CO2 and O2.

14. Xylem and Phloem • The centre of the leaf also contains xylem and phloem tissue arranged into vascular bundles. These vascular bundles form veins that dissect the leaf at regular intervals and supply the leaf with water and nutrients. Figure 8: The xylem delivers water (water vapour) to the photosynthesizing cells. The phloem picks up sugars that have been produced and delivers them to cells throughout the rest of the plant.

15. The Lower Leaf • The lower leaf is critical for the • exchange of gases between the • leaf and the outside • environment. • Guard cells allow for this movement of gases in and out. Guard cells change their shape to control the opening and closing of pores in the leaf, which are called stomata. Guard cells and stomata are significant for transpiration (CO2 enters and oxygen and water vapour exit).

16. The Chloroplast • Chloroplasts are the site of photosynthesis. 6CO2+6H2O+light energy  C6H12O6 + 6O2 • Glucose = C6H12O6 = energy • Oxygen = cellular respiration Thylakoids contain light-trapping chlorophyll molecules. This is the part of the chloroplast where photosynthesis occurs. Thylakoids are arranged in a stack called granum.

20. The Stem • Structure • Xylem vessels are grouped with phloem vessels in vascular bundles • The stem contains most of the xylem tissue, in long fibrous “pipes” • Function • Physical support • Transport of water, nutrients, and sugars phloem xylem

21. The Roots • Roots anchor plants and allow it to take up water and minerals from the soil • Some roots act as a plant’s storage area

22. Types of Roots: Tap & Fibrous

23. The Reproductive OrganThe Flower • The different parts of a flower are specialized leaves. One set is specialized to produce pollen, which manufactures sperm, while another set produces eggs. • Animals and the wind assist plants in pollination.

25. GoldenrodPretty much anywhere you find goldenrod, you can see goldenrod galls. These ball-like formations on the stem of the goldenrod plant are winter homes for the larvae of the Goldenrod Gall Fly (Eurostasolidaginis).

26. GoldenrodThe female fly deposits eggs in the plant stem. The larva secretes chemicals that cause the plant to create a gall. In spring, the larva chews a tunnel to the edge of the gall and then returns to the centre of the gall to pupate.

27. GoldenrodWhen the adult fly emerges, it uses the tunnel to exit the gall. You can find many galls with holes drilled in them over the winter, evidence of a visit from a downy woodpecker or chickadee who has removed the larva and enjoyed a winter snack.

28. Plants Under Attack • Over 400 viruses can infect plants • Not all are harmful, for example the virus that gives Rembrandt tulips their stripes • Plant galls are an abnormal growth of groups of cells produced as a response to attacks from insects, fungi, bacteria and viruses